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diff --git a/Documentation/dev-tools/kunit/running_tips.rst b/Documentation/dev-tools/kunit/running_tips.rst new file mode 100644 index 000000000000..bd689db6fdd2 --- /dev/null +++ b/Documentation/dev-tools/kunit/running_tips.rst @@ -0,0 +1,448 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================ +Tips For Running KUnit Tests +============================ + +Using ``kunit.py run`` ("kunit tool") +===================================== + +Running from any directory +-------------------------- + +It can be handy to create a bash function like: + +.. code-block:: bash + + function run_kunit() { + ( cd "$(git rev-parse --show-toplevel)" && ./tools/testing/kunit/kunit.py run "$@" ) + } + +.. note:: + Early versions of ``kunit.py`` (before 5.6) didn't work unless run from + the kernel root, hence the use of a subshell and ``cd``. + +Running a subset of tests +------------------------- + +``kunit.py run`` accepts an optional glob argument to filter tests. The format +is ``"<suite_glob>[.test_glob]"``. + +Say that we wanted to run the sysctl tests, we could do so via: + +.. code-block:: bash + + $ echo -e 'CONFIG_KUNIT=y\nCONFIG_KUNIT_ALL_TESTS=y' > .kunit/.kunitconfig + $ ./tools/testing/kunit/kunit.py run 'sysctl*' + +We can filter down to just the "write" tests via: + +.. code-block:: bash + + $ echo -e 'CONFIG_KUNIT=y\nCONFIG_KUNIT_ALL_TESTS=y' > .kunit/.kunitconfig + $ ./tools/testing/kunit/kunit.py run 'sysctl*.*write*' + +We're paying the cost of building more tests than we need this way, but it's +easier than fiddling with ``.kunitconfig`` files or commenting out +``kunit_suite``'s. + +However, if we wanted to define a set of tests in a less ad hoc way, the next +tip is useful. + +Defining a set of tests +----------------------- + +``kunit.py run`` (along with ``build``, and ``config``) supports a +``--kunitconfig`` flag. So if you have a set of tests that you want to run on a +regular basis (especially if they have other dependencies), you can create a +specific ``.kunitconfig`` for them. + +E.g. kunit has one for its tests: + +.. code-block:: bash + + $ ./tools/testing/kunit/kunit.py run --kunitconfig=lib/kunit/.kunitconfig + +Alternatively, if you're following the convention of naming your +file ``.kunitconfig``, you can just pass in the dir, e.g. + +.. code-block:: bash + + $ ./tools/testing/kunit/kunit.py run --kunitconfig=lib/kunit + +.. note:: + This is a relatively new feature (5.12+) so we don't have any + conventions yet about on what files should be checked in versus just + kept around locally. It's up to you and your maintainer to decide if a + config is useful enough to submit (and therefore have to maintain). + +.. note:: + Having ``.kunitconfig`` fragments in a parent and child directory is + iffy. There's discussion about adding an "import" statement in these + files to make it possible to have a top-level config run tests from all + child directories. But that would mean ``.kunitconfig`` files are no + longer just simple .config fragments. + + One alternative would be to have kunit tool recursively combine configs + automagically, but tests could theoretically depend on incompatible + options, so handling that would be tricky. + +Setting kernel commandline parameters +------------------------------------- + +You can use ``--kernel_args`` to pass arbitrary kernel arguments, e.g. + +.. code-block:: bash + + $ ./tools/testing/kunit/kunit.py run --kernel_args=param=42 --kernel_args=param2=false + + +Generating code coverage reports under UML +------------------------------------------ + +.. note:: + TODO(brendanhiggins@google.com): There are various issues with UML and + versions of gcc 7 and up. You're likely to run into missing ``.gcda`` + files or compile errors. + +This is different from the "normal" way of getting coverage information that is +documented in Documentation/dev-tools/gcov.rst. + +Instead of enabling ``CONFIG_GCOV_KERNEL=y``, we can set these options: + +.. code-block:: none + + CONFIG_DEBUG_KERNEL=y + CONFIG_DEBUG_INFO=y + CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y + CONFIG_GCOV=y + + +Putting it together into a copy-pastable sequence of commands: + +.. code-block:: bash + + # Append coverage options to the current config + $ ./tools/testing/kunit/kunit.py run --kunitconfig=.kunit/ --kunitconfig=tools/testing/kunit/configs/coverage_uml.config + # Extract the coverage information from the build dir (.kunit/) + $ lcov -t "my_kunit_tests" -o coverage.info -c -d .kunit/ + + # From here on, it's the same process as with CONFIG_GCOV_KERNEL=y + # E.g. can generate an HTML report in a tmp dir like so: + $ genhtml -o /tmp/coverage_html coverage.info + + +If your installed version of gcc doesn't work, you can tweak the steps: + +.. code-block:: bash + + $ ./tools/testing/kunit/kunit.py run --make_options=CC=/usr/bin/gcc-6 + $ lcov -t "my_kunit_tests" -o coverage.info -c -d .kunit/ --gcov-tool=/usr/bin/gcov-6 + +Alternatively, LLVM-based toolchains can also be used: + +.. code-block:: bash + + # Build with LLVM and append coverage options to the current config + $ ./tools/testing/kunit/kunit.py run --make_options LLVM=1 --kunitconfig=.kunit/ --kunitconfig=tools/testing/kunit/configs/coverage_uml.config + $ llvm-profdata merge -sparse default.profraw -o default.profdata + $ llvm-cov export --format=lcov .kunit/vmlinux -instr-profile default.profdata > coverage.info + # The coverage.info file is in lcov-compatible format and it can be used to e.g. generate HTML report + $ genhtml -o /tmp/coverage_html coverage.info + + +Running tests manually +====================== + +Running tests without using ``kunit.py run`` is also an important use case. +Currently it's your only option if you want to test on architectures other than +UML. + +As running the tests under UML is fairly straightforward (configure and compile +the kernel, run the ``./linux`` binary), this section will focus on testing +non-UML architectures. + + +Running built-in tests +---------------------- + +When setting tests to ``=y``, the tests will run as part of boot and print +results to dmesg in TAP format. So you just need to add your tests to your +``.config``, build and boot your kernel as normal. + +So if we compiled our kernel with: + +.. code-block:: none + + CONFIG_KUNIT=y + CONFIG_KUNIT_EXAMPLE_TEST=y + +Then we'd see output like this in dmesg signaling the test ran and passed: + +.. code-block:: none + + TAP version 14 + 1..1 + # Subtest: example + 1..1 + # example_simple_test: initializing + ok 1 - example_simple_test + ok 1 - example + +Running tests as modules +------------------------ + +Depending on the tests, you can build them as loadable modules. + +For example, we'd change the config options from before to + +.. code-block:: none + + CONFIG_KUNIT=y + CONFIG_KUNIT_EXAMPLE_TEST=m + +Then after booting into our kernel, we can run the test via + +.. code-block:: none + + $ modprobe kunit-example-test + +This will then cause it to print TAP output to stdout. + +.. note:: + The ``modprobe`` will *not* have a non-zero exit code if any test + failed (as of 5.13). But ``kunit.py parse`` would, see below. + +.. note:: + You can set ``CONFIG_KUNIT=m`` as well, however, some features will not + work and thus some tests might break. Ideally tests would specify they + depend on ``KUNIT=y`` in their ``Kconfig``'s, but this is an edge case + most test authors won't think about. + As of 5.13, the only difference is that ``current->kunit_test`` will + not exist. + +Pretty-printing results +----------------------- + +You can use ``kunit.py parse`` to parse dmesg for test output and print out +results in the same familiar format that ``kunit.py run`` does. + +.. code-block:: bash + + $ ./tools/testing/kunit/kunit.py parse /var/log/dmesg + + +Retrieving per suite results +---------------------------- + +Regardless of how you're running your tests, you can enable +``CONFIG_KUNIT_DEBUGFS`` to expose per-suite TAP-formatted results: + +.. code-block:: none + + CONFIG_KUNIT=y + CONFIG_KUNIT_EXAMPLE_TEST=m + CONFIG_KUNIT_DEBUGFS=y + +The results for each suite will be exposed under +``/sys/kernel/debug/kunit/<suite>/results``. +So using our example config: + +.. code-block:: bash + + $ modprobe kunit-example-test > /dev/null + $ cat /sys/kernel/debug/kunit/example/results + ... <TAP output> ... + + # After removing the module, the corresponding files will go away + $ modprobe -r kunit-example-test + $ cat /sys/kernel/debug/kunit/example/results + /sys/kernel/debug/kunit/example/results: No such file or directory + +Generating code coverage reports +-------------------------------- + +See Documentation/dev-tools/gcov.rst for details on how to do this. + +The only vaguely KUnit-specific advice here is that you probably want to build +your tests as modules. That way you can isolate the coverage from tests from +other code executed during boot, e.g. + +.. code-block:: bash + + # Reset coverage counters before running the test. + $ echo 0 > /sys/kernel/debug/gcov/reset + $ modprobe kunit-example-test + + +Test Attributes and Filtering +============================= + +Test suites and cases can be marked with test attributes, such as speed of +test. These attributes will later be printed in test output and can be used to +filter test execution. + +Marking Test Attributes +----------------------- + +Tests are marked with an attribute by including a ``kunit_attributes`` object +in the test definition. + +Test cases can be marked using the ``KUNIT_CASE_ATTR(test_name, attributes)`` +macro to define the test case instead of ``KUNIT_CASE(test_name)``. + +.. code-block:: c + + static const struct kunit_attributes example_attr = { + .speed = KUNIT_VERY_SLOW, + }; + + static struct kunit_case example_test_cases[] = { + KUNIT_CASE_ATTR(example_test, example_attr), + }; + +.. note:: + To mark a test case as slow, you can also use ``KUNIT_CASE_SLOW(test_name)``. + This is a helpful macro as the slow attribute is the most commonly used. + +Test suites can be marked with an attribute by setting the "attr" field in the +suite definition. + +.. code-block:: c + + static const struct kunit_attributes example_attr = { + .speed = KUNIT_VERY_SLOW, + }; + + static struct kunit_suite example_test_suite = { + ..., + .attr = example_attr, + }; + +.. note:: + Not all attributes need to be set in a ``kunit_attributes`` object. Unset + attributes will remain uninitialized and act as though the attribute is set + to 0 or NULL. Thus, if an attribute is set to 0, it is treated as unset. + These unset attributes will not be reported and may act as a default value + for filtering purposes. + +Reporting Attributes +-------------------- + +When a user runs tests, attributes will be present in the raw kernel output (in +KTAP format). Note that attributes will be hidden by default in kunit.py output +for all passing tests but the raw kernel output can be accessed using the +``--raw_output`` flag. This is an example of how test attributes for test cases +will be formatted in kernel output: + +.. code-block:: none + + # example_test.speed: slow + ok 1 example_test + +This is an example of how test attributes for test suites will be formatted in +kernel output: + +.. code-block:: none + + KTAP version 2 + # Subtest: example_suite + # module: kunit_example_test + 1..3 + ... + ok 1 example_suite + +Additionally, users can output a full attribute report of tests with their +attributes, using the command line flag ``--list_tests_attr``: + +.. code-block:: bash + + kunit.py run "example" --list_tests_attr + +.. note:: + This report can be accessed when running KUnit manually by passing in the + module_param ``kunit.action=list_attr``. + +Filtering +--------- + +Users can filter tests using the ``--filter`` command line flag when running +tests. As an example: + +.. code-block:: bash + + kunit.py run --filter speed=slow + + +You can also use the following operations on filters: "<", ">", "<=", ">=", +"!=", and "=". Example: + +.. code-block:: bash + + kunit.py run --filter "speed>slow" + +This example will run all tests with speeds faster than slow. Note that the +characters < and > are often interpreted by the shell, so they may need to be +quoted or escaped, as above. + +Additionally, you can use multiple filters at once. Simply separate filters +using commas. Example: + +.. code-block:: bash + + kunit.py run --filter "speed>slow, module=kunit_example_test" + +.. note:: + You can use this filtering feature when running KUnit manually by passing + the filter as a module param: ``kunit.filter="speed>slow, speed<=normal"``. + +Filtered tests will not run or show up in the test output. You can use the +``--filter_action=skip`` flag to skip filtered tests instead. These tests will be +shown in the test output in the test but will not run. To use this feature when +running KUnit manually, use the module param ``kunit.filter_action=skip``. + +Rules of Filtering Procedure +---------------------------- + +Since both suites and test cases can have attributes, there may be conflicts +between attributes during filtering. The process of filtering follows these +rules: + +- Filtering always operates at a per-test level. + +- If a test has an attribute set, then the test's value is filtered on. + +- Otherwise, the value falls back to the suite's value. + +- If neither are set, the attribute has a global "default" value, which is used. + +List of Current Attributes +-------------------------- + +``speed`` + +This attribute indicates the speed of a test's execution (how slow or fast the +test is). + +This attribute is saved as an enum with the following categories: "normal", +"slow", or "very_slow". The assumed default speed for tests is "normal". This +indicates that the test takes a relatively trivial amount of time (less than +1 second), regardless of the machine it is running on. Any test slower than +this could be marked as "slow" or "very_slow". + +The macro ``KUNIT_CASE_SLOW(test_name)`` can be easily used to set the speed +of a test case to "slow". + +``module`` + +This attribute indicates the name of the module associated with the test. + +This attribute is automatically saved as a string and is printed for each suite. +Tests can also be filtered using this attribute. + +``is_init`` + +This attribute indicates whether the test uses init data or functions. + +This attribute is automatically saved as a boolean and tests can also be +filtered using this attribute. |